Earth moving machines, such as wheel loaders and excavators, are designed to perform different operations, such as, but not limited to, digging, dumping, and carrying material from one place to another. A power source, such as an internal combustion engine, provides power to ground engaging members of the machine. The power source also provides power to hydraulic elements of the machine. Generally, a continuously variable transmission is employed in the machine to transmit the power from the power source to the ground engaging members. The transmission of power through the continuously variable transmission is controlled by a control unit.
While performing different operations, the machine may require varying amount of power to operate machine elements, such as hydraulic elements and ground engaging members. Since different operations of the machine may be carried out in different segments of a work cycle, varied amount of power may be required by the hydraulic elements and the ground engaging members in each segment of the work cycle. Such requirement of varied amount of power reduces responsiveness of the machine. Further, when the hydraulic elements require a higher amount of power from the power source during operation, stalling of the power source may occur. As such, operation of the machine may get affected.
U.S. Pat. No. 8,762,014, hereinafter referred as the '014 patent, describes a torque control operation for a transmission. The transmission includes a variable displacement variator with a hydraulic actuator. The transmission is engaged in a neutral state such that the variator output experiences substantially zero torque. A first hydraulic pressure sweep to the hydraulic actuator is commanded while a corresponding sweep of motor speed ratio of the variator is recorded. The transmission is engaged into a locked mode to provide a fixed output speed and a second hydraulic pressure sweep to the hydraulic actuator is commanded, and a corresponding sweep of variator output torque is recorded during this sweep. A torque/pressure map is then constructed relating motor torque, motor speed ratio, and actuator pressure by scaling the sweep of motor speed ratios and the sweep of variator output torque. The resultant map is usable to provide teed forward torque control of the trans mission.
Although the resultant control maps of the '014 patent may improve transmission performance, the variator system may still be less than optimal. In particular, the variator system may not consider all factors affecting transmission performance or be able to adapt to changing performance over a life of the machine.